SA/D ratio really has to do with light air performance and not all that much even then. Once wind force goes to a certain level it has no effect at all. It's about the ability of the boat to generate horse power to drive the boat forward. Lighter boat with more sail area will usually do better in light air say under ten knots. A lot less as wind moves above ten knots and zero or even negative effect when it is time to reef. Hull shape, etc can have a big effect especially when it comes to surfing and to weather.